[AST/Sema/libclang] Replace getSourceRange().getBegin() with getLocStart().
 - getSourceRange().getBegin() is about as awesome a pattern as .copy().size().

I already killed the hot paths so this doesn't seem to impact performance on my
tests-of-the-day, but it is a much more sensible (and shorter) pattern.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152419 91177308-0d34-0410-b5e6-96231b3b80d8
11 files changed